Stability static

intuitively, we can consider a perfectly mixed cloudless atmosphere to have constant 9 and thus it 

Another widely used concept is that of a planetary boundary layer (PBL) in contact with the surface of the Earth above which lies the free atmosphere . The PBL is to some degree a physically mixed layer due to the effects of shear-induced turbulence of convective overturning near the Earth s surface. 

The PBL has different characteristics depending on wind speed and static stability these can be roughly distributed between two extreme categories  

The lapse rate in the PBL is unstable and vertical motion leads to the transport of significant amounts of energy upward, due to the buoyancy of air that has been in contact with the surface. A mixed layer forms up to a height where static stability of the air forms a barrier to thermally induced upward motion. This extreme occurs practically daily over the arid areas of the world and the barrier to upward mixing is often the tropopause itself. On the average in midlatitudes, the unstable or mixed layer is typically 1-2 km deep. 

In between the two extremes of stability and instability, there are numerous near-neutral stability 

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If the acceleration is positive, our parcel is buoyant and spontaneous convection occurs. The atmospheric layer is said to be unstable. Negative acceleration implies that a small displacement, Az, results in the parcel accelerating back toward its initial position and therefore indicates stability. If dP /dz is that for an adiabatic test parcel dT /dz = —gM/Cp and dl/dz that of the existing layer, then for dP/dz > —9.8 K/km is stable and for d7/dz < — 9.8K/km is unstable. The 9.8 K/km figure then provides a simple benchmark for static stability of dry air. 

Bluff-Shaped Projectiles. The static stability drag characteristics of bluff, finless projectile and bomb shapes were discussed in a lecture by Loeb... 

PRINCIPLES OF METEOROLOGICAL ANALYSIS, Walter J. Saucier. Highly respected, abundantly illustrated classic reviews atmospheric variables, hydrostatics, static stability, various analyses (scalar, cross-section, isobaric, isentropic, more). For intermediate meteorology students. 454pp. 6X 9X. 65979-8 Pa. 12.95... 

When a parcel of air in the atmosphere is moved rapidly from an equilibrium condition and its tendency to come back to its undisturbed position is noted, then we term the atmosphere as statically stable. The movement of the packet is considered as impulsive, to preclude any heat transfer from the parcel to the ambience. This tendency of static stability- when exists, is due to the buoyancy force caused by the density differential due to temperature variation with height and such body force acts upon the displaced air-parcel. 

In static stability studies, we do not look for detailed timed-dependent motion of the parcel following the displacement (as the associated accelerations are considered negligible). 

Table 4. Static stabilization at constant length comparison of different copolymers (250 °C, 1 hour)...

The static stability of the air stream usually changes as it moves into and out of the urban area, typically becoming less and more stable, respectively. However it should not be assumed that the boundary layer profiles over the urban area and downwind are identical to the equilibrium states found in neutral, stable and unstable boundary layers over flat terrain. In fact as the flow adjusts characteristic distortions of the air flow profiles occur on these scales, such as blocked flow, unsteady slope flows, gravity currents and boundary layer jets especially near hills, coasts and urban/rural boundaries. These distorted profiles (which are ignored in most mesoscale atmospheric models) significantly affect dispersion (e.g. Hogstrom and Smedman, [274] Owinoh et al., [477]). 

Wood, N Mason, P.(1991) The Influence of Static Stability on the Effective Roughness Lengths for Momentum and Heat Transfer, Q.J.R. Meteorological Society, Vol 117, 1025-1056. 

Figure 12-6. A sketch of the stability diagram for double-diffusive convection. The stability boundary is the solid line ZXW. The dashed line PQ denotes the boundary for static stability where the net density gradient is equal to zero. It is assumed in this sketch that Pr/Sc < 1.

One should constantly recall that a static stability test does not cover those effects likely to be associated with warehousing (in bulk), handling, transportation, display or use. It is essential that other tests cover these aspects to ensure that stability data is not invalidated. This may be done by the use of either laboratory simulated tests or actual field trials . Top pressure (compression) and/or vibration is likely to present one of the more serious hazards. 

With regard to static stability, y, is stable, >2 is unstable, 3 is stable, 4 is unstable and 5 is stable. The bifurcation diagram for this case is shown in Figure 4.6. 

The static stability of a foam refers to the ability of the foam to resist bubble breakdown. The foam s static stability can be quantified by measuring its half-life. This is the time required at static conditions for the foam to drain half of its liquid volume. As parameters such as type of stabilizer, containment pressure, or foam generation process change, the stability will also change. Foam half-life is not a direct measurement of stability. Variations of foam stability will occur under different conditions. 

Stability. The static stability of a foam is the ability to resist bubble breakdown resulting from bubble collapse or coalescence. Foam instability can be caused by the drainage of liquid from the foam resulting from increased quality above 0.95 because of pressure reduction, heating, bubble rupture, or coalescence. 

Half-life tests have shown that the use of gellants increases the static stability of foams, and the use of cross-linkers significantly lengthens half-lives (Figure 10). The figure illustrates the half-lives for different stabilized foams as a function of quality. The addition of gellants and crosslinkers dramatically increase both the viscosity and the static stability of the foam. 

C. F. Wagner and R. D. Evans, Static stability limits and the intermediate condenser station. Report of subcommittee on interconnection and stability factors. AIEE Transactions, 1928, Vol 47, pages 94 to 121. 

The stability parameter a characterizes the dynamic stability limit, which predicts the occurrence of limit cycle oscillations. The safety technical assessment of the dynamic operating behaviour may follow a comparable procedure to that introduced for the evaluation of static stability. As before, the Stanton number, reaction order, and the steady state conversion have to be known. Using these values, Bq can be calculated applying the equation obtained by setting a=0 in Equ. (4-116). 

As has already been demonstrated for the evaluation of static stability, the assessment can also be performed graphically. As an example. Figure 4-23 shows this for the same process of vdiich the static stability was discussed in Figure 4-15 and of which the sensitivity was presented in Figure 4-17. 

On one hand this is quite a desirable situation as it leaves no room for interpretation. On the other hand it has already been outlined in the context of the discussion of static stability that this restricted yes/no statement provides no information on the overall robustness of the process. 

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